OSPF Flood Reduction


You live on a tropical island and work as a network engineer and scientist. After years of study you have discovered a formula so you do not age anymore. Unfortunately your network is running OSPF and LSAs still age…you are wondering if you can do something to OSPF as well.


  • All IP addresses have been preconfigured for you.
  • Configure OSPF on all routers. Achieve both connectivity.
  • Configure OSPF so there is no longer a periodic refresh of LSAs.




OSPF Flood Reduction Network Topology

Video Solution:

Configuration Files

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Written by René Molenaar - CCIE #41726

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About the Author: Rene Molenaar

René - CCIE #41726 is the creator of GNS3Vault.com where he shares CCNA, CCNP and CCIE R&S labs. He also blogs about networking on http://networklessons.com


  1. Apparently this doesn’t affect the ageing out when we filter at an ABR. I attached another router and made “Beach” the ABR between area 0 and 1. After performing an “area 0 filter-list prefix in” the summary entry disappeared from the OSPF database on router Palm.

    My fear was that this would somehow keep us from being able to filter between areas, since it operates by blocking the LSA.

  2. So why does this command stop the aging on some LSAs but not others? I get the commands to make this lab work, but not the concept.

    1. It is configured on a per link basis, so LSAs sent on a given link have the DNA bit set so that all other routers know now to age the LSAs, and effectively disabling the paranoid update.

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